But Dr. Arnold J. Schecter, a University of Texas professor of Environmental and Occupational Health Sciences, says dioxins pose a risk for fetuses, newborns and people with immune deficiencies such as AIDS patients.

“Some people are going to be more susceptible because they receive a higher dose or they’re more sensitive,” says Dr. Schecter, who served on an EPA advisory panel on dioxins.

Dioxins are a class of highly toxic chemicals released into the environment by industrial production, waste incineration and forest fires. The chemicals get into the food chain and accumulate in animal fat.

Air emissions of dioxins in the United States have decreased 90% since 1987, thanks to the EPA, state and industry efforts, the agency said Friday. Even so, some dioxins are now present in every man, woman and child on the planet.

The EPA characterizes dioxins as “likely” carcinogens. They are also linked to developmental and reproductive problems, damage to the immune system, hormone disruption, skin rashes and discoloration, and mild liver damage.

Fetuses and newborns have diets relatively high in fat and their bodies are still developing, putting them at greater risk for health problems related to dioxins, Schecter says, as are people whose immune systems are already compromised.